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Articles 1 - 11 of 11
Full-Text Articles in Engineering
Effect Of Impurities On Performance Of Proton Exchange Membrane Fuel Cell Components, Kitiya Hongsirikarn
Effect Of Impurities On Performance Of Proton Exchange Membrane Fuel Cell Components, Kitiya Hongsirikarn
All Dissertations
It is believed that proton–exchange membrane fuel cells (PEMFCs) are going to be exploited as power generation devices for stationary, automotive, and portable applications in the near future because of their high performance and environmental friendliness. Up to the present, wide spread utilization of PEMFCs is not viable because of their cost and durability in the presence of fuel and oxidant stream impurities. These impurities include NH3, hydrocarbons, CO, CO2, halogenated compounds, cations, etc. The objective of this research was to investigate the effect of these harmful contaminants containing in the H2 fuel stream on …
Circuit Modules For Broadband Cmos Six-Port Systems, Chaojiang Li
Circuit Modules For Broadband Cmos Six-Port Systems, Chaojiang Li
All Dissertations
This dissertation investigates four circuit modules used in a CMOS integrated six-port measurement system. The first circuit module is a wideband power source generator, which can be implemented with a voltage controlled ring oscillator. The second circuit module is a low-power 0.5 GHz - 20.5 GHz power detector with an embedded amplifier and a wideband quasi T-coil matching network. The third circuit module is a six-port circuit, which can be implemented with distributed or lumped- lement techniques. The fourth circuit module is the phase sifter used as calibration loads. The theoretical analysis, circuit design, simulated or experimental verifications of each …
High Frequency Ferromagnetic Inductive Elements For On-Chip Integration And Their Magnetization Dynamics, Hanqiao Zhang
High Frequency Ferromagnetic Inductive Elements For On-Chip Integration And Their Magnetization Dynamics, Hanqiao Zhang
All Dissertations
The dissertation focuses on the broadband characterization of magnetization dynamics of submicron (200-550 nm wide, 10 µm long, 100 nm thick) and micron (2-10 µm wide, 100 µm long, 100 nm thick) size patterned ferromagnetic material (Permalloy, Py) with low frequency and microwave measurement methods. Particularly the ferromagnetic resonance (FMR), damping process, magnetization reversal, mag-noise, and 1/f noise in different pattern geometry, DC current and external magnetic field bias situations are investigated. In addition to simple microwave transmission line measurements, a sensitive on-chip microwave interferometer is proposed and fabricated by means of nano-fabrication techniques. The FMR properties of an individual …
Packet Error Rate Predictive Model For Sensor Radios On Fast Rotating Structures, Lei Tang
Packet Error Rate Predictive Model For Sensor Radios On Fast Rotating Structures, Lei Tang
All Dissertations
Wireless sensing technologies have raised widespread interests in the applications for monitoring fast rotating or moving machinery structures in manufacturing environments. Over the past five years, a few wireless sensor systems have been implemented and proven to feasibly work under fast rotation conditions. However, few of these studies evaluated data transmission performance of the wireless communication systems. Although the manufacturing environments are known to be harsh for wireless communication, in many cases, an excellent data throughput is critical for such systems. Conventional statistical methods for studying wireless communication channels are not sufficient in this specific field.
This dissertation presents systematic …
Studies Relevant To The Design Of Reliable Automotive Electronics, Hua Zeng
Studies Relevant To The Design Of Reliable Automotive Electronics, Hua Zeng
All Dissertations
This dissertation describes three independent studies related to the design of reliable automotive electronics. The topics covered are: the estimation of the radiated emissions from power bus structures, EM propagation of tire pressure monitoring systems (TPMS), and examinations of corrosion-induced faults in a connector.
The first chapter describes a method for estimating the maximum possible radiated emissions from a printed circuit board power bus. An analysis based on a lossy cavity model is performed to determine the maximum possible radiated field corresponding to a given power bus noise voltage. A closed-form expression relating the maximum power bus noise voltage to …
Robust Analysis Of Electromagnetic Responses Of Resonant Structures Using Early-Time And Low-Frequency Data, James Frye, Jr.
Robust Analysis Of Electromagnetic Responses Of Resonant Structures Using Early-Time And Low-Frequency Data, James Frye, Jr.
All Dissertations
The rapid increase of affordable computing resources combined with the continued development and refinement of computational electromagnetic (CEM) methods has yielded a wide range of accurate and well-verified EM modeling tools; however, improvements are required to keep pace with the current and future requirements of EM systems. One such need is the development of robust, computationally-efficient methods which provide one the means to understand complex resonant systems through the by analyzing EM responses. The characteristics of resonant systems often make the determination of a wideband response with CEM methods computationally very intensive. Also, a numerical solution may not directly provide …
Nonlinear Control And Estimation Techniques With Applications To Vision-Based And Biomedical Systems, Nitendra Nath
Nonlinear Control And Estimation Techniques With Applications To Vision-Based And Biomedical Systems, Nitendra Nath
All Dissertations
This dissertation is divided into four self-contained chapters. In Chapter 1, a new estimator using a single calibrated camera mounted on a moving platform is developed to asymptotically recover the range and the three-dimensional (3D) Euclidean position of a static object feature. The estimator also recovers the constant 3D Euclidean coordinates of the feature relative to the world frame as a byproduct. The position and orientation of the camera is assumed to be measurable unlike existing observers where velocity measurements are assumed to be known. To estimate the unknown range variable, an adaptive least squares estimation strategy is employed based …
Protocols For Dynamic Spectrum Access In Cognitive Radio Networks, Steven Boyd
Protocols For Dynamic Spectrum Access In Cognitive Radio Networks, Steven Boyd
All Dissertations
Spectrum access protocols permit secondary users to transmit on frequency bands that are not being utilized by the primary owners. A cognitive radio that wishes to transmit in a band must first decide if the band is available (i.e., not being used by the owner) and then it must periodically re-evaluate the band's availability once it begins transmitting in the band to ensure that a signal from a primary owner has not emerged. To accomplish these tasks, spectrum access protocols employ periodic sensing of the channel. Frequent sensing intervals are required to ensure that cognitive radios wishing to access the …
A Lyapunov Based Approach To Energy Maximization In Renewable Energy Technologies, Erhun Iyasere
A Lyapunov Based Approach To Energy Maximization In Renewable Energy Technologies, Erhun Iyasere
All Dissertations
This dissertation describes the design and implementation of Lyapunov-based control strategies for the maximization of the power captured by renewable energy harnessing technologies such as (i) a variable speed, variable pitch wind turbine, (ii) a variable speed wind turbine coupled to a doubly fed induction generator, and (iii) a solar power generating system charging a constant voltage battery.
First, a torque control strategy is presented to maximize wind energy captured in variable speed, variable pitch wind turbines at low to medium wind speeds. The proposed strategy applies control torque to the wind turbine pitch and rotor subsystems to simultaneously control …
Software Algorithms To Coordinate And Improve Voltage Sag Ridethrough Capabilities Of Networked Industrial Processes, Owen Parks
All Dissertations
For those who design, operate, and troubleshoot industrial processes, electric power quality is a subject that requires much consideration. Processes that use electronic sensors, actuators, and computation devices are heavily reliant on a stable, consistent input power source. When a power quality event such as a voltage fluctuation occurs, automation equipment often behaves unpredictably and causes process malfunction or failure.
Because industrial power consumers often blame their electric utility for these events, some utilities offer process susceptibility studies as a service for their customers. During a typical study, utility technicians and engineers perform in-house tests on suspect components or systems …
Cross-Layer Scheduling Protocols For Mobile Ad Hoc Networks Using Adaptive Direct-Sequence Spread-Spectrum Modulation, Brian Wolf
All Dissertations
We investigate strategies to improve the performance of transmission schedules for mobile ad hoc networks (MANETs) employing adaptive direct-sequence spread-spectrum (DSSS) modulation. Previously, scheduling protocols for MANETs have been designed under the assumption of an idealized, narrowband wireless channel. These protocols perform poorly when the channel model incorporates distance-based path loss and co-channel interference. Wideband communication systems, such as DSSS systems, are more robust in the presence of co-channel interference; however, DSSS also provides multiple-access capability that cannot be properly leveraged with a protocol designed for narrowband systems. We present a new transmission scheduling protocol that incorporates link characteristics, spreading …